spring relief take-up system

[conveyorbud]

I have a chain conveyor with flights that handles various products. The take-up is done with hydraulics but the environment is too harsh. I want to build a take-up that is less forgiving. The hydraulic system, when working, either over slacks or breaks chain. If I get a piece of rebar (foreign object) gets stuck between the chain and the take-up sprocket I want to have it “spring” relieve itself so the chain does not break. This would be similar to the trap metal ejection system in some crushers. I need to maintain chain tension but release when something gets caught between the chain and sprocket then return to the required original tension (after object passes) required to drive the chain. I want to use some type of mechanical take-up with a spring overload system….. I think. Any ideas and ways to calculate it?

 

[dvd]

The take-up tension needs to be sufficient to resist the returning chain and flights since your take-up sprocket is free to move laterally. Typical numbers would be 2.1 times the weight of returning flights and chain multiplied by the chain friction coefficient. You ought to get a copy of this book:

http://cemastore.com/shop/item.asp?itemid=73&catid=3

You should also talk to your chain supplier, they actually may know something about take-ups.

A catenary might be appropriate for a take-up.

You might break chain no matter what, since the foreign object is being carried into the sprocket but the rollers of neighboring links want to run at the pitch diameter so you are trying to absorb the momentum/inertia of the entire return strand of chain and flights. If you have a really dirty process you might try "car wheels" instead of sprockets. The main drawback to this is that the chain isn't locked onto the car wheel by sprocket teeth. If you machined a groove in the car wheel to accept the chain roller then the chain can't float off of the car wheel. There are several unknowns about your particular situation to make it difficult to comment further.

You could explain what type of chain, your flight weight, conveyor speed, can you back-bend the flights, etc. This is just an anonymous forum so good luck and take everything with a grain of salt.

 

[ietech]

Have you considered using a pneumatic take up, not sure if it will work in your environment though. We use the pneumatic take up on very long belt conveyors and it works quite well.

 

[ietech]

Oh, I forgot to mention that you might add a spring, pneumatic, or hydraulic tensioner wheel/pulley/or sprocket in addition to the existing take up.
On some of our conveyors the actual take up is mechanical and the take up pulley is stationary.
Tensioning is controlled by the tensioner pulley. Works well on belt conveyors. Hope this helps.